Spindle Bearing Wear Check

I have been overhauling my Chester DB7 mini-lathe and wondered if anyone could tell me the best way to check if it’s time to replace the spindle bearings. The rotational run-out at the Chuck backplate is 0.01mm and if I put a 30mm bar in the chuck and give it a push 200mm from the chuck I can deflect it 0.1mm. I think the latter is more of a test for the chuck jaws than the spindle bearings, but it gives an idea. Replacing the bearings is a big job and I don’t want to tackle it if it’s not needed. Any advice would be very welcome.

Hi Chris when you push on the bar does it return to zero. Also what is the finnish like, do you have a taper in the work when turning parallel. The bearings are taper type and should be adjustable with care and knowledge.

David

Edited By David George 1 on 03/10/2021 19:49:12

Thanks David, yes the bar returns to zero. I’ve spent a lot of time taking out any twist in the bed and truing up the tailstock, just wondered what was the best way to check the bearings. I thought this lathe had ball bearings and was going to change to angular contact, but if you say they are taper rollers on the DB7, I might just leave it alone! Chris

They are 30206/P5 Bearings if you buy new ones Timken quality are £10.80 each plus vat. Have a look on the Chester hobby web site you can download the manual which lists all parts and information.

David

I was really asking if there is a recommended method of checking the spindle for bearing wear, I’m not at the stage of actually renewing them yet.

Just look at the finish you get

If it cuts good then jobs a good 'un

We're only hobby lathe users

The trouble with pushing a rod held in the chuck is it's unclear what's being measured. It might show the bearings are loose, but maybe not. It's quite easy to be misled, causing one to break the golden rule: 'if it ain't bust, don't fix it!'

I'm in favour of starting with 'does the lathe cut metal OK' before moving on to DTI's and so forth! Are there any signs the lathe isn't cutting correctly? If so what are they? The symptoms may suggest causes other than the bearings. And if the cause isn't obvious, it may be necessary to pin it down by carefully eliminating possibilities one by one.

Dave

Does it get hot? Is it noisy?

Getting hot may just be poor lubrication - too little or too much.

Apart from that, the same as t’others.

Not hot or noisy, I had trouble getting a good finish on a 6” steel shaft between centres but grinding a vertical sheer bit solved that. I think my question has been answered - I’ll leave it alone for now, thanks for the replies.

I tend to keep a look out for cheap decent bearings for various stuff since a spare pair means an almost instant repair when they do need to be done